Selection of, and genetic studies on, mutants manifesting alterations in amount or regulation of glutamine synthetase and/or glutamate synthetase and/or glutamate dehydrogenase in E. coli K12. In vitro studies on regulatory interrelationships among these NH3 assimilatory enzymes. In vitro studies to define any structural association among these NH3 assimilatory enzymes in E. coli K12.